3.1.4.2.1 NBNS Selection
If the application or higher-layer protocol specified a specific interface, then the NBNS list MUST be the NBNS Address List for that interface.
If the application or higher-layer protocol did not specify a specific interface, then the NBNS list MUST be formed by concatenating the NBNS Address List for each interface in the Interface List, in the order the interfaces appear in the Interface List.